Hydrocarbon retainer for drydocks

ABSTRACT

A device placed on the floor of a drydock to encompass the damaged area of the hull of a ship drydocked therein, intercepts the flow of water from the area of the hull during drydocking to filter out hydrocarbons eminating from the damaged hull to preclude contamination of the waters surrounding the drydock and the drydock itself.

Unite States Patent. 1191 1111 3,786,773

Preus Jan. 22, 1974 HYDROCARBON RETAINER FOR 3,702,657 11 1972Cunningham et al. 61/1 F x DRYDOCKS 3,537,587 11 1970 Kain 61/1 F x PaulPreus, PO. Box 1002, Toms River, NJ. 08753 Filed: Sept. 28, 1972 Appl.No: 292,887

Inventor:

US. Cl. 114/45, 61/66 Int. Cl. 1863c 1/02 Field of Search... 114/435,44, 45, 46, 47, 48,

References Cited UNITED STATES PATENTS Jamieson 114/46 PrimaryExaminer-Duane A. Reger Assistant Examiner-Randolph A. Reese Attorney,Agent, or FirmCameron, Kerkam, Sutton, Stowell and Stowell [57] ABSTRACTA device placed on the floor of a drydock to encompass the damaged areaof the hull of a ship drydocked therein, intercepts the flow of waterfrom the area of the hull during drydocking to filter out hydrocarbonseminating from the damaged hull to preclude contamination of the waterssurrounding the drydock and the drydock itself.

8 Claims, 6 Drawing Figures HYDROCARBON RETAINER lFOR DRYDOCKSBACKGROUND OF THE INVENTION In the repair, overhaul and maintenance ofship hulls, the drydock provides a means to provide access to the entiresurface of the hull for accomplishing the necessary work. In the processof drydocking, the ship to be drydocked is floated into the drydock andpositioned over the drydock blocks arranged to conform to and supportthe ships bottom. The water in the drydock is then expelled and the shipcomes to rest on the drydock blocks.

There are two basic types of drydock; the graving dock and the floatingdrydock. The graving dock is fixed and provided with water-tight doorswhich seal the drydock after the ship is positioned so that the watertherein can be pumped out. The floating drydock is provided with waterballast tanks for partly submerging the dock to provide for ship entry,and with pumps for discharging the water ballast from the tanks forfloatation of the dock once the ship is positioned therein. Water in thelatter type of drydock is expelled therefrom by gravity as the drydockis refloated.

Although the invention disclosed herein is equally applicable to boththe aforgoing types of drydocks, it will be described hereinafter asspecifically applied to the latter, floating drydock, for purpose ofillustration.

A problem which has become of increasing importance in recent years ispollution of the environment and not the least noted contributor to thisproblem is pollution by oil spills on waterways. Public reaction andgovernment sanctions have been so severe that such pollution is becomingan important factor in the economic survival of many industrialenterprises.

When a damaged ship requires drydocking for inspection and/or repairsand the fuel or cargo tanks have been damaged, suspected or actualpollution of the waters surrounding the drydocks by oil from damagedtanks is inevitable unless definite preventive steps are taken becausethe great quantities of water expelled from the drydocks drain directlyinto the adjacent waters and will carry any oil contamiments present ordischarged into the drydocks with them.

In the case of collisions or groundings of dry cargo ships, the hazardof oil pollution during subsequent drydocking is great since fuel oil orbunkers is carried in double bottom tanks formed by the bottom hull ofthe ship and spaced, parallel-planar tank tops" or double bottomsdisposed above the bottom hull of the ship. Upon grounding or collision,one or more of these double bottom tanks is almost invariably holed ifthe hull of the ship is penetrated and, upon being holed, that tank isopen to the sea. Although there is an initial escape of oil from a holeddouble bottom tank, the

major portion of the oil in that tank, due to its lower density, ispressed against the tank top and remains in the tank as long as there iswater beneath the ship to keep it there. Upon drydocking, the waterpressure is relieved and the bunkers are discharged into the drydock.Although a major portion of the bunkers could sometimes be removed fromthe damaged double bottom tanks by the ships fuel transfer system, suchremoval is sometimes inadvisable or impossible due to fear ofcontamination of fuel transfer system by sea water, because of loss ofheating capability necessary to render the bunkers pumpable in thedamaged tank or because of the ships fuel transfer capability.

In the cases as described above, oil pollution during drydocking is aserious problem and it is that to which the present invention isdirected.

SUMMARY OF THE INVENTION This invention provides a device forintercepting hydrocarbons escaping from the damaged hull of a shipduring drydocking thereof.

In a preferred embodiment, the invention provides such a devicecomprising a wall structure disposed on the deck of a drydock to extendbeneath the hull of a ship and encompass the damaged portion thereof; atleast a portion of the structure being liquid pervious to pass liquidsflowing from the damaged portion therethrough and an oleophilichydrophobic material associated with the liquid pervious portion toabsorb and retain hydrocarbons from the liquid passing therethrough.

These and many of the attendant advantages and objects of this inventionwill be better understood by those skilled in the art by reference tothe following detailed description when viewed in light of theaccompanying drawings wherein like components throughout the figuresthereof are indicated by like numerals and wherein:

BRIEF DESCRIPTION OF THE DRAWING FIG. I is a perspective view of anembodiment of the invention disposed in a floating drydock.

FIG. 2 is a fragmentary elevational view of a portion of a device inaccordance with the invention.

FIG. 3 is a sectional view of the device of FIG. 2 taken along the lines3-3 thereof.

FIG. 4 is a perspective of the drydock of FIG. I showing a ship in placein the drydock with the drydock submerged.

FIG. 5 is a sectional view taken along the line 55 of FIG. 4.

FIG. 6 is a view similar to FIG. 5 after the water has been expelledfrom the drydock.

DESCRIPTION OF A PREFERRED EMBODIMENT In FIG. 1 an oil containing devicein accordance with the invention is shown generally at 10 mounted on thedeck of a floating drydock 12. The device 10 comprises longitudinal legs14 and 16 running fore and aft on the starboard and portsides of thedrydock and legs 18 and 20 running thwartships the drydock. The legsintersect one another to form a rectangular enclosure beneath what willbe the damaged portion of a ship when placed in the drydock 12. Thelongitudinal legs 14 and 16 are disposed outboard of what will be theturn of the bilge of a ship when placed in a drydock. Drydock blocks 22are disposed on the floor of the drydock 12 to support a ship whenplaced in the drydock in a manner well known in the art. The thwartshiplegs 18 and 20 are of equal height to the drydock blocks-22 at least forthe portion thereof coinciding with the bottom of a ship when placed inthe drydock such that the legs will be in sealing contact with the shipbottom fore and aft of the damaged portion of the ship. The longitudinallegs 14 and 16 as well as the portions of the legs l8 and 20 outboard ofthe ship bottom may be the same height as the afordescribed portions oflegs 18 and 20 if the damage to the ship is confined to the hull bottomitself or may be greater in height if the damage extends above the turnof the bilge as will be described in greater detail below.

FIGS. 2 and 3 are detailed views of the device 10 of FIG. I. It shouldbe understood that the exact form of construction of the device may varyand that the following fabrication details represent a convenient formof construction with materials readily available in a particularshipyard at a particular time. Each of the legs I4 through 20 are ofsubstantially identical construction and the detailed structure setforth here'inbelow should be understood to apply equally to any portionof any of the legs with the variations as may be set forth hereinbelow.The device 10 is attached to the deck of the drydock 12 preferably bywelding vertical members 24 thereto. Top cross members 26 are thenattached, preferably by welding, to the tops of vertical members 24 andthe structure is braced by a stiffleg member 28 attached diagonallybetween the top of one vertical member and the bottom of the adjacentopposed vertical member 24. The stiffleg 28 is preferably angled upwardtoward the interior of the enclosure formed by the legs 14 through 20(FIG. 1) so that the member 24 to which the stiffleg 28 attaches at thetop is disposed on the inside edge of the device 10 to brace the devicetoward the direction of eventual flow as will be described in detailbelow. The members described thusfar are preferably metal and moreparticularly angle iron or a similar readily available structural form.A pair of lower stringers 30 are attached to the lower ends of thevertical member 24 on the drydock floor 12. A pair of upper stringers 32are attached to the upper ends of the same vertical members. Meshnetting 34, preferably 541 inch mesh hardware cloth wire, is attachedbetween the stringers to form perforate sides and a top for the device10. A bouyant oil absorbent, water repellant material 36, having aneffective partical dimension sufficient to be retained by the mesh 34,is disposed in the confines formed by the mesh 34. Petroleum absorbentmaterial marketed by Clean Water, Inc. of Toms River, NJ. under thetrademark, Sorbent C, has proven ideal for the purpose of thisinvention. At suitable intervals along the length of each leg of thedevice 10, 8 foot intervals for example, cross stringers 38 are attachedbetween the upper stringers 32 and between the lower stringers 30 towhich mesh netting 40 is attached to serve to longitudinally divide thelegs and preclude migration of the absorbent material 36 duringoperation of the device as described below. The above describedstringers are preferably formed from planking such, for example, as 2 X12 inch planks, the netting 34 and 40 being attached thereto by nails,staples or the like.

In operation, and with reference now specifically to FIGS. 4, and 6, aship 42 is brought into the drydock l2 and is positioned over thedrydock blocks 22 so that a damaged portion of the hull 44 (FIGS. 5 and6) is positioned within the confines of the device 10.

As can be seen in FIG. 5 double bottom tanks 46 containing the shipsfuel oil or bunkers" 48, are disposed in the bottom of the hull of theship 42. The damaged portion 44 has ruptured one of these tanks 46 and aportion of the bunkers 48 has been displaced and replaced by sea water50. Since oil is less dense than water, the bunkers 48 in the rupturedtank 46 are pressed against the tank top and are retained in the upperportion of the tank. The oil absorbent material 36, because of itsbouyancy and water repellant characteristics, floats to the top of thedevice as the drydock is submerged and remains there, pressed againstthe top mesh of the device, so long as the drydock is submerged.

In FIG. 6, the drydock 12 has been refloated bringing the ship 42 out ofthe water for repair. The water in the drydock is discharged as thedrydock is raised, through the open end thereof. As this water isdischarged, the oil or bunkers 48 in the damaged tank 46 drains fromthat tank and flows, with the water level beneath the tank, toward theopen ends of the drydock. As the water level drops in the drydock, theoil absorbent material 36 also follows the water level thereby remainingin a blocking position relative to the path the oil being dischargedfrom the holed tank 46 must take to leave the area of the hull damage.As the oil and water reach the blocking position assumed by the oilabsorbent material 36, the oil is absorbed at this point and effectivelyfilteredf from the-water flowing through the device 10 thereby retainingall of the 'oil in the absorbent material and/or within the confines ofthe device 10 while allowing all of the water to drain from the drydockwithout pollution of surrounding waters.

In actual use a device incorporating this invention, as reported in theUS. Coast Guard s Environmental Protection Newsletter, February, 1972(Vol. 1, No. 1), the M/V Singapore Trader was successfully drydockedwithout any overboard discharge of bunker fuel although a considerableamount of fuel was discharged onto the drydock floor within the confinesof the device.

Although the device 10 is illustrated having a water perviousconstruction throughout the entire perimeter thereof, it should beunderstood that portions thereof may be formed as a water tight wallwith water pervious box portions interspersed along the length thereofas required. The primary feature that must be considered in such designis that the oil absorbent material 36 be present in sufficient quanityto absorb the full amount of oil expected to be discharged from theship. Absorbent C petroleum absorbent material has an absorbtioncapability of about 0.55 gallons of bunker C per pound of absorbentmaterial and, utilizing the probable capacity of the damaged tanks, thequantity of material needed can readily be determined beforehand.

What has been set forth herein is intended as exemplary of a teaching inaccordance with the invention to aid those skilled in the art in thepractice thereof.

What is new and desired to be protected by Letters Patent of the UnitedStates is:

l. A device for retaining hydrocarbons discharged from the damaged hullof a ship during drydocking thereof comprising:

a drydock a wall structure extending upwardly from the floor of saiddrydock to define an enclosure to extend beneath the hull of said shipand encompass the damaged portion thereof, at least a portion of saidwall structure being liquid pervious to pass all liquid flowing from thedamaged portion of said hull therethrough; and means associated withsaid device to retain hydrocarbons in the liquid passing therethrough.

2. A device in accordance with claim I wherein the portion of said wallstructure coinciding with the bottom of said ship is configured to makesealing contact length of about inch disposed in said enclosure.

6. A device in accordance with claim 5 wherein said 1 mesh is about #4inch in size.

7. A device in accordance with claim 5 wherein said material is oflesser volume than said mesh enclosure and is disposed to follow thewater line of the water in said drydock within the limits of saidenclosure.

8. A device in accordance with claim 5 wherein said material is placedin said enclosure in quantities of about 2 pounds for every gallon ofhydrocarbon to be discharged.

1. A device for retaining hydrocarbons discharged from the damaged hullof a ship during drydocking thereof comprising: a drydock a wallstructure extending upwardly from the floor of said drydock to define anenclosure to extend beneath the hull of said ship and encompass thedamaged portion thereof, at least a portion of said wall structure beingliquid pervious to pass all liquid flowing from the damaged portion ofsaid hull therethrough; and means associated with said device to retainhydrocarbons in the liquid passing therethrough.
 2. A device inaccordance with claim 1 wherein the portion of said wall structurecoinciding with the bottom of said ship is configured to make sealingcontact with said hull to preclude flow of liquid between said hull andsaid wall structure.
 3. A device in accordance with claim 1 wherein saidmeans includes a buoyant oleophilic-hydrophobic material in said liquidpervious portion.
 4. A device in accordance with claim 3 wherein saidliquid pervious portion of said wall structure comprises a meshenclosure for containing said oleophilic-hydrophobic material therein.5. A device in accordance with claim 4 wherein saidoleophilic-hydrophobic material comprises a loose mass of fiberousmaterial having an effective fiber length of about 1/8 inch disposed insaid enclosure.
 6. A device in accordance with claim 5 wherein said meshis about 1/4 inch in size.
 7. A device in accordance with claim 5wherein said material is of lesser volume than said mesh enclosure andis disposed to follow the water line of the water in said drydock withinthe limits of said enclosure.
 8. A device in accordance with claim 5wherein said material is placed in said enclosure in quantities of about2 pounds for every gallon of hydrocarbon to be discharged.